Intrinsic multiferroicity and magnetoelectric coupling in VSI2 monolayer

Two dimensional (2D) multiferroic materials have great potential for miniaturized electronic and high-density multi-states data storage devices due to the coexistence of electric and spin polarization. Because the origins of magnetism and ferroelectricity are mutually exclusive and difficult to coexist, there are still rare to date 2D multiferroic semiconductors with good performance. Here, we propose a 2D multiferroic material, VSI2 monolayer, which has both ferromagnetic and ferroelectric properties by first principles calculation. It shows robust ferroelectricity with an appropriate switching barrier (similar to 140 meV), and the in-plane ferroelectric polarization is 1.44 x 10(-10) C/m. At the same time, the VSI2 monolayer magnetic easy axis is along the b-axis direction and owns a large magnetic anisotropy energy (MAE) (512 mu eV/V-ion). Based on Monte Carlo simulations of the Heisenberg model, the Curie temperature (T-C) is calculated to be approximately 92 K. In addition, biaxial strain can significantly change the MAE, and the in-plane magnetic easy axis can be switched to the out-of-plane direction by 5% biaxial tensile strain. In particular, we can change the magnetic moment at the two ends of VSI2 nanoribbons by switching the direction of electric polarization, providing an opportunity for the application of magnetic-electric control and memory devices. Our theoretical prediction provides a good platform for studying the 2D multiferroic effects and spintronic properties.